Year level: 4

Strand: Number

Lesson length: 60 mins

In this lesson, students will use mathematical modelling to make decisions based on the purchasing of gifts. Students will explore different ways to estimate and form possible options for purchasing, ensuring they do not go over budget.

### Achievement standard

Students use mathematical modelling to solve financial and other practical problems, formulating the problem using number sentences, solving the problem, choosing efficient strategies and interpreting results in terms of the situation.

### Content descriptions

Students use mathematical modelling to solve practical problems involving additive and multiplicative situations including financial contexts; formulate the problems using number sentences and choose efficient calculation strategies, using digital tools where appropriate; interpret and communicate solutions in terms of the situation. AC9M4N08

### General capabilities

Numeracy:

Critical and Creative Thinking:

• Analysing (Interpret concepts and problems)
• Inquiring (Identify, Process and Evaluate information)
• Observe the working out in students' workbooks while they are developing a plan or solving the problem and make notes on what you observe.
• Listen to students' discussions with each other regarding their strategy choices.
• Notice the level of difficulty based on the student’s choice of strategy. Did students change their strategy after the summarise stage? Did they select a more efficient strategy?
• Use estimation approaches to make an estimate.
• Estimate approximate money values of multiples of items.
• Follow steps for problem-solving and know problem-solving strategies they could use to find solutions.
• Calculate multiple money amounts.
• Use relevant strategies to calculate the difference between money values involving dollars and cents.
• Adopt a growth mindset and persist with a problem they do not have an immediate solution for.

Some students may:

• find moving from additive to multiplicative thinking when calculating costs of the same item purchased multiple times (repeated addition to multiplication)
• find shifting to abstract thinking difficult – estimation is an approximate value, not an exact value
• need to move from inefficient to efficient strategies that are embedded in their learning
• have challenges reading and understanding the problem – there is choice in the way the money can be distributed, and students must decide to purchase items based on their value and how much money they have in total (the problem doesn’t state that the amount spent on each person is of equal value or that the amount that remains unspent).